Brazilian Grand Prix, Interlagos
Qualifying: Saturday 1600 Race: Sunday 1700 Coverage: BBC Radio 5 Live, BBC Sport website and ITV1
Hamilton's preparations were disrupted by some poor weather
Felipe Massa gained the upper hand on rival Lewis Hamilton after practice for the Brazilian Grand Prix, where both aim to win the 2008 world championship.
There was little to separate the duo in the first session as Massa topped the timesheets by just 0.190 seconds.
But in a damp second practice Hamilton trailed in ninth, well behind Massa who was second to Fernando Alonso.
McLaren's Hamilton has a seven-point lead over Ferrari's Massa ahead of Sunday's title decider at Interlagos.
"Our car was blindingly quick this morning despite the cold weather, which made the track feel quite slippery," said the Englishman.
"The car felt good. I'm pretty comfortable that we have a good package.
"This afternoon, we focused on our race pace - but we were interrupted by the threat of rain and the changeable wind direction.
"I'm positive that the changes we've made will put us in a good position for tomorrow."
After failing to match the McLarens for pace in the last race in China, Massa felt optimistic following the early run-out in Brazil.
"For sure we are more competitive, and when you are more competitive there is more motivation," he said. "It was a good start."
Massa added: "My aim is to be in front of everyone, both tomorrow and on Sunday. Then we can do the math when it's over."
Hamilton held the same seven-point advantage over Ferrari's Kimi Raikkonen going into last season's finale in Brazil only to see the title slip through his fingers.
His race came unstuck when he lost ground by running wide on the first lap before falling to the back of the field because of a gearbox problem.
Though Hamilton recovered to seventh, Raikkonen took the chequered flag to snatch the title by a single point.
With one hand on the world championship for the second season running, Hamilton only needs to finish fifth in Brazil if Massa wins his home race.
WHAT HAMILTON NEEDS TO DO
If Massa wins in Brazil, Hamilton must finish at least fifth to be champion
If Massa is second, Hamilton must finish at least seventh
If Massa is third or lower, Hamilton is champion regardless of his result in Brazil
The McLaren team are determined not to jeopardise Hamilton's title chances by pushing for victory at Interlagos but in first practice the two title rivals were evenly matched.
With scattered spots of rain falling, the Englishman set the pace with his second effort of 1:12.495.
But with nine minutes left on the clock, Massa shaved off a little more time to eclipse Hamilton's benchmark by 0.190 secs and take top spot.
The Brazilian continued to dominate on his hometown circuit in Sao Paolo in the afternoon session.
He seized first place from Toyota's Jarno Trulli at the third time of asking, setting a benchmark of 1:12.353.
Another rain shower came at the wrong time for Hamilton to make any impression on the pace-setters.
The McLaren driver was out on the softer tyres but diminishing track temperatures saw him mired down the field.
Hamilton's attempt to put together the perfect lap was not helped by several lock-ups, with the McLaren driver coming unstuck at the Bico de Pato and in the Senna S combination.
He aborted his last flying lap and finished down in ninth place, nearly half a second off Massa's time.
Alonso, who had been conspicuously quiet during practice, suddenly unleashed his pace in the dying minutes of practice to topple Massa.
The Renault driver, who won the 2005 and 2006 world titles at Interlagos, edged out the Brazilian by just 0.057 secs on his way to the day's best flying lap of 1:12.296.
Ferrari's Raikkonen set the third fastest time in first practice despite a series of spins and was fourth fastest in the afternoon.
It was a disappointing day for fellow Finn Heikki Kovalainen in the second McLaren as he followed up his fifth placing in the morning with 15th in the late session.
The cooler than usual conditions in Sao Paolo seemed to confuse team tactics across the board and more rain is forecast for Sunday's race.
First free practice times for the Brazilian Grand Prix:
1. Felipe Massa (Brz) Ferrari 1 min 12.305 secs
2. Lewis Hamilton (GB) McLaren-Mercedes 1:12.495
3. Kimi Raikkonen (Fin) Ferrari 1:12.507
4. Robert Kubica (Pol) BMW Sauber 1:12.874
5. Heikki Kovalainen (Fin) McLaren-Mercedes 1:12.925
6. Fernando Alonso (Spa) Renault 1:13.061
7. Mark Webber (Aus) Red Bull-Renault 1:13.298
8. Nelson Piquet (Brz) Renault 1:13.378
9. Nick Heidfeld (Ger) BMW Sauber 1:13.426
10. Timo Glock (Ger) Toyota 1:13.466
11. Jarno Trulli (Ita) Toyota 1:13.600
12. Nico Rosberg (Germany) Williams-Toyota 1:13.621
13. Sebastien Bourdais (Fra) Toro Rosso-Ferrari 1:13.649
14. Rubens Barrichello (Brz) Honda 1:13.676
15. Jenson Button (GB) Honda 1:13.766
16. Kazuki Nakajima (Jpn) Williams-Toyota 1:13.806
17. Sebastian Vettel (Ger) Toro Rosso-Ferrari 1:13.836
18. David Coulthard (GB) Red Bull-Renault 1:13.861
19. Adrian Sutil (Ger) Force India- Ferrari 1:14.704
20. Giancarlo Fisichella (Ita) Force India-Ferrari 1:14.821
Second practice times:
1. Alonso 1:12.296
2. Massa 1:12.353
3. Trulli 1:12.435
4. Raikkonen 1:12.600
5. Webber 1:12.650
6. Vettel 1:12.687
7. Piquet 1:12.703
8. Rosberg 1:12.761
9. Hamilton 1:12.827
10. Nakajima 1:12.886
11. Coulthard 1:12.896
12. Kubica 1:12.971
13. Heidfeld 1:13.038
14. Glock 1:13.041
15. Kovalainen 1:13.213
16. Barrichello 1:13.221
17. Bourdais 1:13.273
18. Button 1:13.341
19. Sutil 1:13.428
20. Fisichella 1:13.691